The production of phosgene by the reaction of chlorine with carbon monoxide in the presence of a carbon catalyst is a well known process. The phosgene produced by this process will typically contain 400 to 500 ppm by weight carbon tetrachloride. This amount, evaluated on the basis of the total world-wide production of phosgene of about ten billion pounds (4.5.times.10.sup.9 kg) corresponds to co-production of about 4 to 5 million pounds (1.8.times.10.sup.6 kg to 2.3.times.10.sup.6 kg) of carbon tetrachloride with the phosgene.
Japanese patent publication (Kokoku) No. Hei 6[1994]-29129 discloses that the amount of carbon tetrachloride produced during the phosgene manufacturing process can be reduced (e.g., by about 50%) by using an activated carbon which has been washed with an acid and which contains a total of 1.5 wt. % or less of metal components comprised of transition metals, boron, aluminum and silicon.
A process for producing phosgene using carbon having an active metal content of less than 1000 ppm and a weight loss of about 12% or less in the WVC temperature test has been described (see U.S. application Ser. No. 60/012,021 and International Application No. PCT/US96/17526).
Carbon tetrachloride has been of concern in connection with ozone depletion and global warming potentials. Therefore, there is an interest in developing phosgene processes in which the amount of carbon tetrachloride impurity is minimized.